Stator and insulating bobbin and a manufacturing method of the stator

ABSTRACT

An insulating bobbin mounted on a tooth extending from an annular yoke of a stator with a rectangular wire being around the insulating bobbin has a tooth insulating portion for insulating the tooth of the stator and the rectangular wire and an extending portion extending from an end portion of the tooth insulating portion along an inner surface of the yoke, wherein a guide groove for guiding the rectangular wire diagonally relative to a circumferential direction of the tooth insulating portion from an outside of the extending portion is provided in a side of the extending portion on one of axial sides of the stator.

[0001] The present invention claims foreign priority to Japanese patentapplication no. 2003-146420 filed on May 23, 2003 and no. 2003-181369filed on Jun. 25, 2003, the contents of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a stator for use in rotationalelectric machines such as electric motors and generators, an insulatingbobbin for the stator and a manufacturing method of the stator.

[0004] 2. Description of the Related Art

[0005] Windings for stators include a winding made up of so-called roundwire having a circular cross section and a winding made up of so-calledrectangular wire having a substantially rectangular cross section.

[0006] While the round wire produces a space therebetween even when thewire is wound tightly, the rectangular wire is advantageous over theround wire in that the former can be aligned so as not to produce anyspace therebetween whereby the space factor can be improved. When usedherein, the space factor means a ratio between the cross-sectional areaof the slot and an area occupied by the coil wire, and an increase inspace factor increase the performance of the rotational electricmachine.

[0007] The winding formed by winding the rectangular wire is disclosed,for example, in a Japanese Patent UnexaminedPublicationJP-A-2000-245092.

[0008] When forming a stator winding by winding a rectangular wire in analigned fashion, however, since the surface of the stator winding soformed becomes substantially flat, when the stator winding on anoutermost layer protrudes, the stator winding on the outermost layermoves in a widthwise direction, causing a risk that a desired shapecannot be maintained (refer to FIG. 28, a detailed description beingprovided later on).

[0009] On the other hand, Japanese Patent Unexamined PublicationJP-A-2001-359250 (refer to paragraph No. 0006 and FIG. 14) proposes atechnique for preventing the deviation of a rectangular wire byrestricting a widthwise movement of the rectangular wire by holdingportions being formed on the rectangular wire so as to protrudetherefrom.

[0010] Thus, while the rectangular is advantageous in that the spacefactor can be increased, the rectangular becomes easy or difficult to bebent depending on a direction of its bending. So-called flat-wisebending in which the rectangular wire is bent in a thickness-wisedirection thereof provides an easy bending, whereas so-called edgewisebending in which the rectangular wire is bent in a widthwise directionthereof provides a difficult bending. There may be caused a problem tointroduce the rectangular wire into an insulating bobbin due to thebending properties of the rectangular wire.

[0011]FIG. 17 shows a rectangular wire introducing portion in aconventional insulating bobbin and a start-winding portion of arectangular wire introduced. In an insulating bobbin 100, extendingportions 102, 103 are provided at both ends of a tooth insulatingportion being formed in a rectangular tubular shape, and an introductionsupport portion 104 is provided in an outer side of one 102 of theextending portions.

[0012] In a case where a rectangular wire 110 is introduced from anoutside in an axial direction of the insulating bobbin 100 while athickness-wise direction of the rectangular wire 110 is positioned so asto intersect at right angles with a plane-wise direction of a horizontalside 110 a of the tooth insulating portion 101, so that the rectangularwire 110 passes through a groove 104 a in the introduction supportportion 104 and a groove 102 a in the extending portion 102 to be woundalong a vertical side 101 b of the tooth insulating portion 101, therectangular wire has to be bent at right angles in the groove 102 a inthe extending portion 102.

[0013] In this case, as shown in FIG. 17, when attempting to bend therectangular wire in the groove 102 a using the flat-wise bending, atwist is caused in a bent portion of the rectangular wire 110, and thebent portion that is expanded due to the twist so caused interferes witha winding of an upper layer such as a second layer or upper.

[0014] On the other hand, as shown in the same drawing, when winding therectangular wire for an upper layer while avoiding an interference withthe bent portion, a large space (a gap) where there does not exist anywinding is produced as shown in FIG. 18, and hence there is caused adrawback that the space factor is decreased.

[0015] On the other hand, when bending the rectangular wire 110 in thegroove 102 a using the edgewise bending, such a bending cannot beimplemented with a common winding machine, and therefore, a windingmachine having a special construction is required, which increases theproduction costs. In addition, when using the edgewise bending, sincethe radius of curvature of the bent portion becomes smaller, there mayalso be caused a risk that the insulating layer of the winding isdamaged.

[0016] Also, In the aforesaid conventional technique, since the holdingportions are formed on the rectangular wire, a special shape is requiredwhich is different from conventional ones, and this calls for acomplicated rectangular wire forming process. In addition, since thesize of the rectangular wire is increased due to the provision of theholding portion, there is caused a problem that a decrease in spacefactor is called for.

SUMMARY OF THE INVENTION

[0017] The present invention was made to provide a stator and aninsulating bobbin which can allow for a smooth introduction of arectangular wire into the insulating bobbin and which can increase thespace factor of the rectangular wire so introduced.

[0018] Further, the invention was made in view of these situations, andan object thereof is to provide a stator which can increase the spacefactor of a stator winding that is formed by winding a rectangular wireand which can maintain the desired shape of the stator winding tothereby enhance the reliability thereof and a method for fabricating thestator.

[0019] With a view to solving the problem, according to a first aspectof the invention, there is provided an insulating bobbin mounted on atooth extending from an annular yoke of a stator with a rectangular wirebeing around the insulating bobbin, having a tooth insulating portioninsulating the tooth of the stator and the rectangular wire and anextending portion extending from an end portion of the tooth insulatingportion along an inner surface of the yoke, wherein a guide grooveguiding the rectangular wire diagonally relative to a circumferentialdirection of the tooth insulating portion from an outside of theextending portion is provided in a side of the extending portion on oneof axial sides of the stator.

[0020] According to the construction, since the rectangular wire can beinserted diagonally from an outside of the extending portion of theinsulating bobbin, the rectangular wire can be smoothly wound around thetooth insulating portion on a first turn thereof without edgewisebending the rectangular wire.

[0021] In addition, the twisting or forcible bending of the rectangularwire at the portion where the rectangular wire is introduced into thetooth insulating portion 21 can be prevented.

[0022] According to a second aspect of the invention, there is providedan insulating bobbin as set forth in the first aspect of the invention,wherein a an inclination angle of the guide groove relative to thecircumferential direction of the tooth insulating portion is set equalto or larger than an angle 0 which is expressed by the followingequation;

θ=tan⁻¹(Ww/Wt)

[0023] wherein Ww represents a width of the rectangular wire, and Wtrepresents a width of the tooth insulating portion.

[0024] According to the construction, since there is no risk that thestart-winding portion of the first layer is expanded due to curving orbending, the production of a thick winding can be prevented which wouldotherwise be caused in the event that the rectangular wire for thesecond layer comes to interfere with the start-winding portion of thefirst layer when the rectangular wire for the second layer is started tobe wound around the tooth insulating portion.

[0025] According to a third aspect of the invention, there is providedan insulating bobbin as set forth in the first or aspect of theinvention, wherein a bottom surface of the guide groove is made up of aninclined surface which inclines inwardly in the axial direction of thestator as the bottom surface approaches the tooth insulating portionalong a longitudinal direction of the guide groove.

[0026] According to the construction, the degree of freedom of directionin which the rectangular wire is introduced is expanded.

[0027] According to a fourth aspect of the invention, there is providedan insulating bobbin as set forth in the third aspect of the invention,wherein where the bottom surface of the guide groove is made up of aninclined surface which inclines inwardly in the axial direction of thestator as the bottom surface approaches the tooth insulating portionalong a widthwise direction of the guide groove, and wherein the bottomsurface of the guide groove connects continuously to a side of the toothinsulating portion without any difference in level.

[0028] According to the construction, the degree of freedom of directionin which the rectangular wire is introduced is expanded further.

[0029] According to a fifth aspect of the invention, there is providedan insulating bobbin as set forth in the first aspect of the invention,wherein an intersection point between an inner side of the extendingportion and an outer side of the guide groove is positioned outwardly ofa side of the tooth insulating portion where the rectangular wire isbent for the first time by a distance equal to or larger than athickness of the rectangular wire.

[0030] According to the construction, when a first turn of therectangular wire is wound around the tooth insulating portion, therectangular wire can be wound therearound closely to the inner side ofthe extending portion without producing no gap between the wire and theinner side.

[0031] According to a sixth aspect of the invention, there is providedan insulating bobbin as set forth in the first aspect of the invention,wherein a height of a highest point of a line of intersection between arectangular wire for a first layer and a rectangular for a second wireis set equal to or smaller than a height being 1.5 times as large as thethickness of the rectangular wire from the side of the tooth insulatingportion.

[0032] According to the construction, the rectangular wire of the secondlayer can ride over the rectangular wire of the first layer in a smoothfashion.

[0033] According to a seventh aspect of the invention, there is provideda stator having an insulating bobbin mounted on a tooth extending froman annular yoke of a stator with a rectangular wire being around theinsulating bobbin, including a tooth insulating portion for insulatingthe tooth of the stator and the rectangular wire and an extendingportion extending from an end portion of the tooth insulating portionalong an inner surface of the yoke, wherein a guide groove for guidingthe rectangular wire diagonally relative to a circumferential directionof the tooth insulating portion from an outside of the extending portionis provided in a side of the extending portion on one of axial sides ofthe stator, wherein the teeth are provided of an annular yoke atpredetermined intervals in a circumferential direction, wherein theinsulating bobbin is mounted on each of the teeth so provided, andwherein a rectangular wire is wound around the insulating bobbin somounted.

[0034] According to the construction, there can be obtained a statorwhich can provide an extremely high space factor of rectangular wire.

[0035] According to an eighth aspect of the invention, there is providedan insulating bobbin as set forth in the first aspect of the invention,wherein the rectangular wire for an outermost layer is extendeddiagonally from a start-winding position thereof on one edge side of theinsulating bobbin toward the other edge side thereof to the followingline so as to straddle a space equivalent to one line so as to provide arecessed portion and then wound around a plurality of turns to form adiagonal extending portion, and thereafter is wound across the diagonalextending portion in a direction in which the rectangular wirediagonally intersects with the diagonal extending portion so as to bewound into the recessed portion.

[0036] According to this aspect of the invention, the space factor canbe increased by winding the rectangular wire concentratedly in analigned fashion. In addition, while the external surface of the statorwinding becomes substantially flat by winding the rectangular wireconcentratedly in an aligned fashion, by winding the rectangular wirefor the outermost layer in such a manner as to form the diagonalextending portion and thereafter winding the same rectangular wire insuch a manner as to diagonally intersect with the diagonal extendingportion to thereby be wound into the recessed portion, the winding thatis wound across the diagonal extending portion after the formationthereof is allowed to be accommodated in the recessed portion to therebyrestrict the widthwise direction of the winding. Furthermore, since thewinding is wound around in such a manner that the portion of therectangular wire that is wound into the recessed portion and the portionthereof that forms the diagonal extending portion are wound around insuch a manner as to intersect with each other, the widthwise movement ofthe portions are restricted by each other, thereby making it possible tomaintain the shape of the stator winding to the desired shape thereof.

[0037] According to a ninth aspect of the invention, there is providedan insulating bobbin as set forth in the first aspect of the invention,wherein a chamfered portion is formed at a corner portion of the bobbinand a tapered portion is provided on an inside of the chamfered portion.

[0038] According to this aspect of the invention, since the rectangularwire that is wound around in the recessed portion can be guided by thechamfered portion formed on the corner portion and the tapered portionprovided on the inside of the chamfered portion, the winding work can byperformed more smoothly. Furthermore, the insulating bobbin can be madelighter in weight and smaller in size by forming the chamfered portion.According to a tenth aspect of the invention, there is provided a methodfor manufacturing a stator including an insulating bobbin having a toothinsulating portion insulating the tooth of the stator and therectangular wire, an extending portion extending from an end portion ofthe tooth insulating portion along an inner surface of the yoke and aguide groove guiding a rectangular wire diagonally relative to acircumferential direction of the tooth insulating portion from anoutside of an extending portion on one of axial sides of the stator,comprising steps of providing a plurality of teeth on the stator atpredetermined intervals in a circumferential direction thereof, mountinginsulating bobbins on the plurality of teeth, winding concentratedly arectangular wire around the insulating bobbin in an aligned fashion,causing a rectangular wire for an outermost layer to extend diagonallyfrom a start-winding position thereof on one edge side of the insulatingbobbin toward the other edge side thereof to the following line so as tostraddle a space equivalent to one line so as to provide a recessedportion and then winding the rectangular wire a plurality of turns toform a diagonal extending portion and winding the rectangular wire sodiagonally extended across the diagonal extending portion in a directionin which the rectangular wire diagonally intersects with the diagonalextending portion so as to be wound into the recessed portion.

[0039] According to this aspect of the invention, by winding therectangular wire concentratedly in an aligned fashion, the space factorcan be increased, and by winding the rectangular wire across thediagonal extending portion in such a manner as to diagonally intersecttherewith so as to be wound into the recessed portion, the widthwisemovement of the winding can be restricted by the recessed portion, andthe widthwise movement of the portion of the rectangular wire that iswound into the recessed portion and the portions thereof that form thediagonal extending portion is restricted by each other, thereby makingit possible to maintain the shape of the rectangular wire to the desiredshape thereof.

[0040] According to an eleventh aspect of the invention, there isprovided an insulating bobbin mounted on a tooth extending from anannular yoke of a stator with a rectangular wire being around theinsulating bobbin, having a tooth insulating portion insulating thetooth of the stator and the rectangular wire and an extending portionextending from an end portion of the tooth insulating portion along aninner surface of the yoke, wherein a guide groove guiding therectangular wire to the outside is provided in a side where theend-winding end of the rectangular portion is located.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1 is an overall cross-sectional view of a stator according toa first embodiment of the invention;

[0042]FIG. 2 is a front view showing a state in which a rectangular wireis wound around an insulating bobbin that is used in the stator of thefirst embodiment;

[0043]FIG. 3 is a cross-sectional view taken along the line III-III inFIG. 2;

[0044]FIG. 4 is a cross-sectional view taken along the line IV-IV inFIG. 2;

[0045]FIG. 5 is a drawing for explaining a minimum angle of a guidegroove relative to a tooth insulating portion;

[0046]FIG. 6 is a drawing for explaining an intersection point betweenan outer side of the guide groove and an inner surface of an extendingportion;

[0047]FIG. 7 is a drawing for explaining an intersection point betweenan outer side of the guide groove and an inner surface of an extendingportion in a comparison example;

[0048]FIG. 8 is a perspective view of a second embodiment of aninsulating bobbin according to the invention;

[0049]FIG. 9 is a cross-sectional view of the insulating bobbinaccording to the second embodiment, which corresponds to FIG. 4;

[0050]FIG. 10 is a perspective view of a third embodiment of aninsulating bobbin according to the invention;

[0051]FIG. 11 is a perspective view of the insulating bobbin accordingto the third embodiment;

[0052]FIG. 12 is a drawing showing a specific example, which is morerealistic, of the insulating bobbin according to the third embodiment,which is a front view showing a state in which a rectangular wire iswound around the insulating bobbin;

[0053]FIG. 13 is a cross-sectional view taken along the line XIII-XIIIin FIG. 12;

[0054]FIG. 14 is an enlarged cross-sectional view showing a main part ofFIG. 13;

[0055]FIG. 15 is a front view of an insulating bobbin according toanother embodiment;

[0056]FIG. 16 is a front view of an insulating bobbin according to afurther embodiment;

[0057]FIG. 17 is a perspective view showing a portion where arectangular wire is introduced and a start-winding portion of aconventional insulating bobbin;

[0058]FIG. 18 is a side view of the conventional insulating bobbin;

[0059]FIG. 19 is a cross-sectional view schematically illustrating astator according to an embodiment of the invention;

[0060]FIGS. 20A-20E are explanatory drawings illustrating a process offorming a stator winding on a stator piece shown in FIG. 19;

[0061]FIGS. 21A-21F are explanatory drawings illustrating anotherprocess of forming a stator on the stator piece shown in FIG. 19;

[0062]FIG. 22 is a plan view of a stator piece on which the windingprocess shown in FIG. 20 is implemented;

[0063]FIG. 23 is a partial explanatory drawing of a stator on which thewinding process shown in FIG. 21 is implemented;

[0064]FIG. 24 is a perspective view showing insulating bobbin pieceswhich constitute an insulating bobbin;

[0065]FIG. 25 is a plan view showing a state in which the stators shownin FIG. 23 are assembled together;

[0066]FIG. 26 is a plan view showing a state in which the stators shownin FIG. 24 are assembled together;

[0067]FIGS. 27A-27E are process drawings illustrating a process ofwinding a rectangular wire to a stator piece of a comparison example;

[0068]FIG. 28 is a plan view of a stator on which the winding processshown in FIG. 27 is implemented; and

[0069]FIG. 29 is a plan view illustrating a state where the statorsshown in FIG. 28 are assembled together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0070] Embodiments of stators and insulating bobbins according to theinvention will be described below by reference to FIGS. 1 to 16.

[0071] [First Embodiment]

[0072] Firstly, a first embodiment of a stator and an insulating bobbinaccording to the invention will be described below by reference to FIGS.1 to 7.

[0073] As shown in FIG. 1, a stator 1 is constructed by connecting aplurality of stator modules 2 in an annular shape and is adapted for usein rotational electric machines such as electric motors and generators.

[0074] Each stator module 2 includes a stator core 10 made up of a yokeportion 11 and a tooth portion (a tooth) 12, an insulating bobbin 20mounted on the tooth portion 12 of the stator core 10 and a rectangularwire 50 wound around the insulating bobbin 20.

[0075] The yoke portions 11 of the respective stator cores 10 areconnected together so as to form an annular yoke 1 a of the stator 1. Inorder to ease the connection of the yoke portions 11, an engaging convexportion 11 a is provided on a circumferential end face of the yokeportion, and an engaging concave portion 11 b is provided on the otherend face thereof for fitting on the engaging convex portion 11 a.

[0076] The tooth portion 12 is formed so as to have a substantiallyrectangular cross section an extends from the center of the yoke portion11 toward the radial center of the stator 1. An extending portion 13extending in a circumferential direction of the yoke portion 11 isprovided at a distal end of the tooth portion 12.

[0077] As shown in FIGS. 2 to 4, the insulating bobbin 20 includes atooth insulating portion 21 formed into a rectangular tubular shape andextending portions 22, 23 which extend from axial end portions of thetooth insulating portion 21 along an inner surface of the yoke portion11. The tooth insulating portion 21 is disposed so as to surround sidesof the tooth portion 12, the extending portion 22 is disposed along aninner surface of the extending portion 13 of the stator core 10, and theextending portion 23 is disposed along an inner circumferential surfaceof the yoke portion 11.

[0078] A rectangular wire introducing guide groove 24 is provided on aside of the extending portion 22 which is on one of axial sides of thestator 1, and the rectangular wire 50 is introduced into the toothinsulating portion 21 through the guide groove 24 from an outside of theextending portion 22 for being wound around a side of the toothinsulating portion 21. Note that, as shown in FIG. 6, the rectangularwire 50 is started to be wound from a side 21 a on the one of the axialsides of the stator 1 and is wound to a side 21 b on one ofcircumferential sides of the stator 1. Namely, the rectangular wire 50is bent on this side 21 b for the first time.

[0079] To describe the guide groove 24 in detail by reference to FIGS. 5and 6, a bottom surface 24 a of the guide groove 24 is formed so as tobe flush with the side 21 a of the tooth insulating portion 21, and thewidth of the bottom surface 24 a is set slightly larger than the width Wof the rectangular wire 50. The guide groove 24 is inclined diagonallyin the longitudinal direction relative to the circumferential directionof the tooth insulating portion 21 (in other words, in a planardirection of an inner surface 22 a of the extending portion 22), and theinclination angle thereof is set equal to or larger than an angle θ,which is expressed by the following equation and equal to or smallerthan 30°;

[0080] θ=tan⁻¹ (width W of the rectangular wire/width L of the toothinsulating portion).

[0081] The reason why the inclination angle is set in the range isbecause a portion of the rectangular wire 50 which is before astart-winding portion of a first turn of the rectangular wire 50constitutes an interruption when a second turn of the rectangular wire50 is wound around the tooth insulating portion 21, in case theinclination angle is set smaller than θ, whereas in case the inclinationangle is set larger than 30°, a bent portion that is produced when therectangular wire 50 is started to be wound around the tooth insulatingportion 21 is expanded, causing a problem in winding the rectangularwire 50 for a second layer or upper.

[0082] Furthermore, as shown in FIG. 6, an intersection point P betweenthe inner surface 22 a of the extending portion 22 and an outer side 24b of the guide groove 24 is set to be positioned outwardly of the side21 b of the tooth insulating portion 21 where the rectangular wire isbent for the first time by a distance D equal to (or larger than) thethickness of the rectangular wire 50, whereby, when a first turn of therectangular wire 50 is wound around the tooth insulating portion 21, therectangular wire 50 can be wound therearound closely to the innersurface 22 a without no gap being produced between the wire and theinner surface 22 a of the extending portion 22, thereby making itpossible to enhance the space factor.

[0083]FIG. 7 is a drawing illustrating a comparison example, and asshown in the drawing, in the event that an intersection point P′ betweenan inner surface 22 a of an extending portion 22 and a guide groove 24is positioned closer to the center than the intersection point P, whenthe first turn of the rectangular wire is wound along the side 21 b ofthe tooth insulating portion 21, a gap is produced between therectangular wire 50 and the inner surface 22 a of the extending portion22, this decreasing the space factor.

[0084] In the insulating bobbin 20 that is constructed as has beendescribed heretofore, since the rectangular wire 50 can be inserteddiagonally from the outside of the extending portion 22 of theinsulating bobbin 20 with a bottom side of the rectangular wire 50 beingmade flush with the side 21 a of the tooth insulating portion 21, therectangular wire 50 does not have to be bent edgewise, and the firstturn of the rectangular wire 50 can be smoothly wound around the sides21 a, 21 b of the tooth insulating portion 21. Consequently, a windingoperation using a simple winding machine is made possible.

[0085] In addition, since the first turn of the rectangular wire 50 canbe smoothly wound around the sides 21 a, 21 b of the tooth insulatingportion 21, the necessity is obviated of twisting or forcibly bendingthe rectangular wire 50 at the portion where the rectangular wire 50 isintroduced into the tooth insulating portion 21, which has been carriedout conventionally, and hence there is eliminated a risk that aninsulating layer formed on the surface of the rectangular wire 50 isdamaged.

[0086] Additionally, since there is caused no forcible bending on therectangular wire 50 at the portion where the rectangular wire 50 isintroduced into the tooth insulating portion 21 and on the first turn ofthe rectangular wire 50, there is eliminated a risk that the introducingportion and the first turn of the rectangular wire 50 interfere with asecond turn of the rectangular wire 50 when winding the rectangular wire50 on the second turn, and as shown in FIG. 3, there is no risk that alower layer interferes with an upper layer when winding the rectangularwire 50 for a third layer or upper, whereby the space factor can beenhanced.

[0087] Consequently, in the stator 1 having the insulating bobbin 20,the space factor of the rectangular wire 50 can be increased extremelyhigh.

[0088] [Second Embodiment]

[0089] Next, referring to FIGS. 8 and 9, a second embodiment of a statorand an insulating bobbin according t the invention will be described.Note that FIG. 8 is a perspective view showing a half of an insulatingbobbin 20, and FIG. 9 is a drawing corresponding to FIG. 4 whichillustrates the first embodiment.

[0090] A stator 1 and an insulating bobbin 20 according to the secondembodiment differ from those of the first embodiment only in that abottom surface 24 a of a guide groove 24 in the insulating bobbin 20 ismade up of an inclined surface which inclines inwardly in the axialdirection of the stator 1 as it extends along the longitudinal directionof the guide groove 24 so as to approach the tooth insulating portion21. Since the other constructions are identical to those of the firstembodiment, like reference numerals are given to like constituent parts,and the description thereof will be omitted.

[0091] Namely, the bottom surface 24 a of the guide groove 24 is neitherflush nor parallel with the side 21 a of the tooth insulating portion21, and the bottom surface 24 a of the guide groove at an initiating end(an end farther apart from the tooth insulating portion 21) thereof ispositioned more outside in the axial direction of the stator 1 than thebottom surface 24 a of the guide groove 24 at a terminating end (an endcloser to the side 21 b of the tooth insulating portion 21). In otherwords, assuming that the side 21 a of the tooth insulating portion 21 isa reference plane, the bottom surface 24 a of the guide groove 24 at theinitiating end thereof is made higher than the bottom surface 24 a atthe terminating end when measured from the reference plane.

[0092] According to the construction, the degree of freedom of directionin which the rectangular wire 50 is introduced is expanded, and as aresult, the degree of freedom in designing the insulating bobbin 20 isexpanded.

[0093] Note that as has been described above, in the event that thebottom surface 24 a of the guide groove 24 is made up of the inclinedsurface which inclines inwardly in the axial direction of the stator 1as it extends along the longitudinal direction of the guide groove 24 soas to approach the tooth insulating portion 21, when winding therectangular wire 50 along the inner surface of the extending portion 22for a second layer, the rectangular wire 50 so wound needs to ride overthe rectangular wire 50 wound for the first layer. A height over whichthe rectangular wire 50 needs to ride then becomes a height, resultingwhen measured from the reference plane (the side 21 a), of a highestpoint (namely, a point A in this embodiment) of a line of intersection(also referring to FIG. 2, from point A to point B) between therectangular wire 50 that is wound along the inner surface of theextending portion 22 for the first layer and the rectangular wire 50 forthe second layer.

[0094] In the event that the ride-over height is too high, therectangular wire 50 for the second layer cannot ride over therectangular wire of the first layer in a smooth fashion, resulting in acause for a disturbance of winding.

[0095] As to the riding over of the first layer rectangular wire by thesecond layer rectangular wire, it is found out that in case a heightfrom the reference plane (the side 21 a) at the point A is restricted toa height that is 1.5 times or smaller the thickness D of the rectangularwire 50, the rectangular wire 50 for the second layer can smoothly rideover the rectangular wire 50 of the first layer, causing no disturbancein winding. Then, as shown by solid lines in FIG. 9, it is preferable toset the inclination angle of the bottom surface 24 a such that theheight, resulting when measured from the reference plane (the side 21a), of the highest point (point A) of the line of intersection isrestricted to the height that is 1.5 times or smaller than the thicknessD of the rectangular wire 50.

[0096] [Third Embodiment]

[0097] Next, referring to FIGS. 10 to 14, a third embodiment of a statorand an insulating bobbin according to the invention will be describedbelow.

[0098] As shown in FIGS. 10 and 11, a stator 1 and an insulating bobbin20 according to the third embodiment differ from those of the firstembodiment only in that a bottom surface 24 a of a guide groove 24 inthe a bottom surface 24 a of a guide groove 24 in the insulating bobbin20 is made up of an inclined surface which inclines inwardly in theaxial direction of the stator 1 as it extends along the longitudinaldirection of the guide groove 24 so as to approach the tooth insulatingportion 21 and which inclines inwardly in the axial direction of thestator 1 as it extends along a widthwise direction of the guide groove24 so as to approach the tooth insulating portion 21, and that thebottom surface 24 a of the guide groove 24 connects continuously to theside 21 a of the tooth insulating portion 21 without any difference inlevel being produced therebetween.

[0099] Since the other constructions are identical to those of the firstembodiment, like reference numerals are given to like constituent parts,and the description thereof will be omitted.

[0100] As has been described as to the second embodiment, when thebottom surface 24 a of the guide groove 24 in the insulating bobbin 20is made to incline inwardly in the axial direction of the stator 1 as itextends along the longitudinal direction of the guide groove 24 so as toapproach the tooth insulating portion 21, it is preferable to restrictthe height, resulting when measured from the reference plane (the side21 a), of the highest point (point A) of the line of intersectionbetween the rectangular wire 50 that is wound along the inner surface ofthe extending portion 22 for the first layer and the rectangular wire 50for the second layer to the height that is 1.5 times or smaller than thethickness D of the rectangular wire 50. However, in case the conditionis attempted to be satisfied, as shown in double-dashed lines in FIG. 9,the inclination angle of the bottom surface 24 a of the guide groove 24cannot be increased, resulting in restriction of the degree of freedomin designing the insulating bobbin 20.

[0101] Then, according to the third aspect of the invention, by causingthe bottom surface 24 a of the guide groove 24 to incline furtherinwardly in the axial direction of the stator as it extends along thewidthwise direction of the guide groove 24 so as to approach the toothinsulating portion 21 (in other words, by causing the height of thebottom surface 24 a from the reference plane (the side 21 a) to lower asit extends along the widthwise direction of the guide groove 24 so as toapproach the tooth insulating portion 21), the height from the referenceplane (the side 21 a) at the highest point (point A) of the line ofintersection can be allowed to be restricted to the height which isequal to or smaller than 1.5 times the thickness D of the rectangularwire 50, even when the inclination angle is increased which inclinesinwardly in the axial direction of the stator as it extends along thelongitudinal direction of the guide groove 24 so as to approach thetooth insulating portion.

[0102]FIG. 12 is a drawing showing a specific example, which is morerealistic, of the insulating bobbin 20 according to the thirdembodiment, which shows a state in which the winding of the rectangularwire 50 around the insulating bobbin 20 is completed, FIG. 13 is across-sectional view taken along the line XIII-XIII in FIG. 12, and FIG.14 is an enlarged cross-sectional view showing a main part of FIG. 13.In this specific example, after the rectangular wire 50 has been woundaround the insulating bobbin 20, the introducing portion (the portionwhich is inserted into the guide groove 24) of the rectangular wire 50is bent to the outside of the extending portion 22 so as to be locked toa support portion of the insulating bobbin 20, and the terminating endportion of the rectangular wire 50 is bent to the outside of theextending portion 23 so as to be locked to a support portion 26 of theinsulating bobbin 20.

[0103] Note that, as shown in FIGS. 15 and 16, a guide groove 27 may beprovided on the insulating bobbin 20 on a side where the end-winding endof the rectangular portion 50 is located for guiding the rectangularwire 50 to the outside of the insulating bobbin 20. FIG. 15 shows anexample where the guide groove 24 located at the start-winding end ofthe rectangular wire 50 is provided in the extending portion 22, whereasthe guide groove 27 at the end-winding end of the rectangular wire 50 isprovided in the extending portion 23, and FIG. 16 shows an example whereboth the guide groove 24 located at the start-winding end and the guidegroove 27 at the end-winding end are provided in the extending portion22.

[0104] A stator and a method for fabricating the same according to anembodiment of the invention will be described below by reference to theaccompanying drawings. FIG. 19 is a schematic view showing theconstruction of a stator according to an embodiment of the invention.

[0105] Hereinafter, the stator according to the embodiment of theinvention will be described by reference to the drawings. FIG. 19 is aperspective view of a stator core according to the embodiment of theinvention. As is shown in the drawing, the stator core 1001 is formedinto an annular shape by arranging a plurality of stator pieces 1002 ina circumferential direction. Each stator piece 1002 has a plurality ofmagnetic pole teeth 1003 a which are formed so as to protrude radiallyinwardly of the stator core 1001 and a yoke portion 1003 b which isformed so as to extend in the circumferential direction of the statorcore 1001.

[0106] A locking portion 1020 protruding circumferentially outwardly isprovided on the magnetic pole tooth 1003 a of the stator piece 1002 atan end portion on an inner circumferential side thereof so as to preventa stator winding 7, which will be described later on, from falling offthe tooth in a radially inward direction. On the other hand, an engagingconcave portion 1004 and an engaging convex portion 1005 are provided oncircumferential ends of the yoke portion 1003 b of the stator piece1002, whereby the yoke portions 1003 b, 1003 b of adjacent stator pieces1002 can be positioned and held so positioned by bringing the engagingconcave portions 1004 into engagement with the engaging convex portions1005 of the yoke portions 1003 b, respectively.

[0107] The stator piece 1002 is formed by stacking electromagnetic steelplates such as a silicone steel plates having a directional property,and for example, in the magnetic pole tooth 1003 a, an easilymagnetizable direction is set in the radial direction of the stator core1001, and in the yoke portion 1003 b, the easily magnetizable directionis set in the circumferential direction of the stator core 1001.

[0108] In addition, a stator winding 1007 made up of a conductive wireof copper or the like is wound around sides of the magnetic pole teeth1003 a which are arranged in the annular shape, respectively. In thisembodiment, so-called rectangular wire 1006 having a substantiallyrectangular cross section is wound around each tooth 1003 a byconcentrated winding so as to form the stator winding 1007. This will bedescribed later on.

[0109] A tubular insulating bobbin 8 is disposed between the statorwinding 1007 and each tooth 1003 a. In this embodiment, a pair of bobbinpieces 1008 a, 1008 b are combined into a tubular shape as an insulatingbobbin 1008.

[0110]FIG. 24 is a perspective view showing the insulating bobbin piece1008 a which constitutes the insulating bobbin 1008. As shown in thedrawing, the insulating bobbin piece 1008 a has a main body portion 1017that is formed into a shape having a substantially U-shaped crosssection so as to cover the sides of the magnetic pole tooth 1003 a, atooth-side extending portion 1018 and a yoke-side extending portion1019, both of which extend from respective ends of the main body portion1017. The tooth-side extending portion 1018 is a location which extendsalong the locking portion 1020 of the magnetic pole tooth 1003 a, andthe yoke-side extending portion 1019 is a location which extends alongan inner circumferential surface of the yoke portion 1003 b.

[0111] Additionally, an inner circumferential side holding portion 1009and an outer circumferential side holding portion 1010 are formed,respectively, on a radially inner circumferential side and a radiallyouter circumferential side of the stator core 1001 for holding endportions of the stator winding 1007. In this embodiment, a start-windingportion of the stator winding 1007 is held in the inner circumferentialside holding portion 1009, whereas an end-winding portion of the statorwinding 1007 is held in the outer circumferential side holding portion1010, respectively. In addition, a guide portion 1011 is formed on thetooth-side extending portion 1018 in such a manner as to incline at apredetermined angle from the inner circumferential side holding portion1009, so that the rectangular wire 1006 can be wound while being guidedby the guide portion 1011.

[0112] Additionally, a chamfered portion 1012 is formed on a cornerportion of the yoke side extending portion 1019 of the insulating bobbinpiece 1008 a, and a tapered portion 1013 is provided on an inside of thechamfered portion 1012, so that the rectangular wire can be wound whilebeing guided by the tapered portion 1013. This will be described lateron.

[0113] Note that the other bobbin piece 8 b which constitutes theinsulating bobbin 1008 is constructed such that a main body portion 1017thereof is formed into a substantially symmetrical shape to that of theinsulating bobbin piece 1008 a, as shown in FIG. 24, except that holdingstructures such as the inner circumferential side holding portion 1009and the outer circumferential side holding portion 1010 for holding theend portions of the stator winding 1007 are omitted from a tooth-sideextending portion 1018 and a yoke-side extending portion 1019 thereof.

[0114] The pair of insulating bobbin pieces 1008 a, 1008 b which areformed as has been described above are made to face each other and arethen mounted on each magnetic pole tooth 1003 a in such a manner as tofit thereon from both sides in an axial direction of the stator core1001, whereby the sides of the magnetic pole tooth 1003 a are covered bythe main body portions 1017 of the insulating bobbin pieces 1008 a, 1008b, an inner circumferential surface of the yoke portion 1003 b iscovered by the yoke-side extending portions 1019 of the insulatingbobbin pieces 1008 a, 1008 b, and the locking portion 1020 of themagnetic pole tooth 1003 a is covered by the tooth-side extendingportions 1018 of the insulating bobbin pieces 1008 a, 1008 b,respectively.

[0115] Then, in this state, the rectangular wire 1006 is wound aroundthe sides of each magnetic pole tooth 1003 a by concentrated winding soas to form the stator winding 1007. FIGS. 20A to 20E are explanatorydrawings illustrating a process of forming the stator winding 1007 ontothe stator piece 1002 shown in FIG. 19.

[0116] Firstly, as shown in FIG. 20A, a start-winding portion 1007-1S ofa stator winding 1007-1 for a first layer is held in the innercircumferential side holding portion 1009 of the insulating bobbin 1008.Then, by winding the stator winding 1007 around along the guide portion1011 of the insulating guide bobbin 1008 in an aligned fashion from aradially inward end to a radially outward end of the insulating bobbin1008 sequentially, the stator winding 1007-1 is formed. In thisembodiment, when the stator winding 1007-1 which is wound around alongthe guide portion 1011 extends from one edge side (a left side in FIG.20A) to the other edge side (a right side in FIG. 20A) of the insulatingbobbin 1008, the stator winding 1007-1 is wound in such a manner as todeviate radially outwardly by a distance equal to the width of therectangular wire 1006, whereby the end-winding portion 1007-1E can bepositioned in a space equal to the width of the rectangular wire 1006secured on the one edge side (the left side in FIG. 20A) while thestator winding 1007-1 for the first layer is being brought into abutmentwith the yoke-side extending portion 1019 of the insulating bobbin 1008on the other edge side (the right side in FIG. 20A) thereof.

[0117] Next, as shown in FIG. 20B, a start-winding portion of a statorwinding 1007-2 is wound from the same position as the end-windingportion 1007-1E of the first layer along the yoke-side extending portion1019 and is further wound from the radially outward end to the radiallyinward end of the insulating bobbin 1008 in a linearly aligned fashion.Then, the stator winding 1007-2 is wound around the insulating bobbin1008 in such a manner as to become substantially horizontal relative toan upper end of the guide portion 1011, and an end-winding portion1007-2E of the stator winding 1007-2 is positioned on one edge side (aleft side in FIG. 20B) of the insulating bobbin 1008.

[0118] Next, as shown in FIG. 1002C, when extending from the one edgeside to the other edge side of the insulating bobbin 1008, a statorwinding 1007-3 for a third layer is wound in such a manner as to deviateradially outwardly by the distance equal to the width of the rectangularwire 1006 in a similar way to that shown in FIG. 20A, whereby anend-winding portion 1007-3E of the stator winding 1007-3 for the thirdlayer is positioned in a space equal to the width of the rectangularwire 1006 secured on the one edge side of the insulating bobbin 1008while the stator winding 1007-3 is being brought into abutment with theyoke-side extending portion 1019 of the insulating bobbin 1008 on theother edge side thereof.

[0119] Then, as shown in FIG. 20D, a stator winding 1007-4 for a fourthlayer is formed. The stator winding 1007-4 is caused to diagonallyextend from a start-winding portion 1007-4S located on the one edge sideof the insulating bobbin 1008 toward the other edge side thereof to thefollowing line in such a manner as to straddle a space equivalent to oneline so as to provide a recessed portion and is then wound around aplurality of turns (three times in this case) to thereby form a diagonalextending portion 1014, and an end-winding portion 1007-4E1 ispositioned on the one edge side of the insulating bobbin 1008 where thestart-winding portion 1007-4S is positioned.

[0120] Then, as shown in FIG. 20E, a start-winding portion 1007-5S of astator winding 1007-5 for a fifth layer is wound diagonally across thediagonal extending portion 1014 in such a manner as to intersectdiagonally therewith, and the stator winding 1007-5 for the fifty layeris wound into the recessed portion 1015, whereby the stator winding1007-5 is made to fall in the fourth layer. Then, this stator winding1007-4 is wound from the recessed portion 1015 along the outercircumferential side holding portion 1010, so that an end-windingportion 1007-4E2 is held in the outer circumferential side holdingportion 1010.

[0121] According to the construction, the widthwise movement of thestator winding (1007-5S to 1007-4E) of the outermost layer isrestricted, and hence the desired shape can be maintained. This will bedescribed by reference to FIGS. 27, 28. FIG. 27 shows a process ofwinding a rectangular wire around a stator piece of a comparisonexample. FIG. 28 is a plan view of the stator piece on which the windingprocess shown in FIG. 27 has been implemented. In FIGS. 27A to 27C, therectangular wire is wound sequentially in an aligned fashion from aradially inward end to a radially outward end or from the radiallyoutward end to the radially inward end as was so done in FIGS. 20A to20C. Then, as shown in FIGS. 27D, 27E, the rectangular wire is woundsequently from the radially outward end to the radially inward end, andwhen a start-winding portion 1007-5S of a fifth layer is caused toextend on a stator winding 1007-4 located radially outwardly so as to bewound therearound, the stator winding 1007-5 so wound protrudes from thesurrounding stator winding 1007-4. Since there is provided norestriction to a widthwise movement of the stator winding 1007-5 whichso protrudes, the stator winding 1007-5 is permitted to move in thewidthwise direction, and hence there is caused a risk that the overallshape of the stator winding 1007 (1007-1 to 1007-5) cannot be held tothe desired shape.

[0122] In contrast, with the stator winding 1007 according to theembodiment, the rectangular wire (1007-5S to 1007-4E2) of the outermostlayer is made to intersect diagonally with the diagonal extendingportion 1014 so as to be wound into the recessed portion 1015, wherebythe rectangular wire (1007-5S to 1007-4E2) of the outermost layer can beaccommodated in the recessed portion 1015 so as to restrict thewidthwise movement thereof. Furthermore, since the portion (1007-5S to1007-4E2) of the rectangular wire that is wound into the recessedportion 1015 and the portions (1007-4) thereof which constitute thediagonal extending portion 1014 are wound around in such a manner as tointersect with each other, the widthwise movement of the respectiveportions can be restricted by each other, and consequently, the shape ofthe stator winding 1007 can be maintained to the desired shape.Furthermore, by winding the rectangular wire 1006 along the insulatingbobbin 1008 mounted on the magnetic pole tooth 1003 a in theconcentratedly aligned fashion, the space factor can be increased. Inaddition, since there is no need to apply any special treatment orprocessing to the rectangular wire 1006, the costs, the number ofprocessing steps and processing time can be suppressed to lower levels,respectively.

[0123]FIG. 21 illustrates another process of forming a stator winding onthe stator piece shown in FIG. 19. In FIGS. 21A to 21C, the rectangularwire is wound sequentially in an aligned fashion from the radiallyinward end to the radially outward end or from the radially outward endto the radially inward end as was so done in FIGS. 20A to 20C. Then, asshown in FIG. 21D, the rectangular wire is caused to extend from astart-winding portion 1007-4S1 on one edge side of the insulating bobbin1008 to the other edge side thereof in such a manner as to straddle aspace equivalent to one line so as to form a recessed portion 1015 andis then wound diagonally around the insulating bobbin 1008 twice tothereby form a diagonal extending portion 1014. Following this, as shownin FIG. 21E, the rectangular wire is wound across diagonally thediagonal extending portion 1014 in such a manner as to diagonallyintersect therewith and is wound into the recessed portion 1015.Furthermore, as shown in FIG. 21F, the rectangular wire is wound furtherfrom the one edge side of the insulating bobbin 1008 along the outercircumferential side holding portion 1010, and thereafter, anend-winding portion 1007-5E is held in the outer circumferential holdingportion 1010. According to the construction, since the diagonalextending portion 1014 and the portion (1007-5S to 1007-4E2) which ismade to intersect diagonally with the diagonal extending portion 1014 soas to be wound into the recessed portion 1015 can be pressed down by thestator winding 1007-5 that is wound along the outer circumferential sideholding portion 1010, the shape of the stator winding 1007 can bemaintained more rigidly. In addition, as shown in FIG. 21F, the statorwinding 1007-5 of the outermost layer can be held at the same level asthat of another stator winding 1007-4 on the one edge side (a left sidein FIG. 21F) of the insulating bobbin 1008, whereby the widthwisemovement thereof is restricted.

[0124] In addition, since the rectangular wire 1006 that is wound intothe recessed portion 1015 can be guided by the chamfered portion 1012formed on the corner portion of the bobbin 1008 and the tapered portion1013 provided on the inside of the chamfered portion 1012, the windingwork can be implemented more smoothly. This will be described byreference to FIGS. 22, 23 and 28. FIGS. 22, 23 and 28 are plan views,respectively, of the stator pieces 1002 on which the winding processesshown in FIGS. 20, 21, 27 have been implemented. As shown in thesedrawings, in a case where the diagonal extending portion 1014 is formedwith the recessed portion being provided (in the case of FIGS. 20, 21),when compared with a case where no recessed portion 1015 is provided (inthe case of FIG. 28), while the inclination angle of the rectangularwire 1006 wound around the outermost layer is increased, the windingwork can be performed more smoothly by allowing the rectangular wire1006 to be guided by the tapered portion 1013 provided on the chamferedportion 1012 of the insulating bobbin 1008. Furthermore, the insulatingbobbin 1008 can be attempted to be made lighter in weight and lower incosts by forming the chamfered portion 1012.

[0125]FIGS. 25, 26, 29 are plan views showing, respectively, stateswhere the stator pieces 1002 shown in FIGS. 22, 23, 28 are assembledtogether. As shown in these drawings, being different from the statorpieces 1002 (FIG. 29) of the comparison example, the stator pieces 1002(FIGS. 22, 23) according to the embodiment can be assembled togetherwhile maintaining the stator winding 1007 in the desired shape, and thereliability is increased. In addition, the stator pieces 1002 shown inFIG. 26 is preferred to the stator pieces 1002 shown in FIG. 25 in thata wider gap can be secured between the stator windings 1007 of thestator pieces 1002.

[0126] Note that the contents of the invention are, of course, notlimited to the embodiment that has been described heretofore. Forexample, as has been described above, while it is preferable to form thetapered portion 1013 and the chamfered portion 1012 on the insulatingbobbin 1008, the shape of the bobbin 1008 is not limited thereto.

[0127] While there has been described in connection with the preferredembodiments of the present invention, it will be obvious to thoseskilled in the art that various changes and modification may be madetherein without departing from the present invention, and it is aimed,therefore, to cover in the appended claim all such changes andmodifications as fall within the true spirit and scope of the presentinvention.

[0128] According to the first aspect of the invention, since therectangular wire can be inserted diagonally from an outside of theextending portion of the insulating bobbin, the rectangular wire can besmoothly wound around the tooth insulating portion on a first turnthereof without edgewise bending the rectangular wire, and winding workusing a simple winding machine is made possible. In addition, since thetwisting or forcible bending of the rectangular wire at the portionwhere the rectangular wire is introduced into the tooth insulatingportion 21 can be prevented, no damage is given to an insulating surfacethat is formed on the surface of the rectangular wire.

[0129] According to the second aspect of the invention, since there isno risk that the start-winding portion of the first layer is expandeddue to curving or bending, the production of a thick winding can beprevented which would otherwise be caused in the event that therectangular wire for the second layer comes to interfere with thestart-winding portion of the first layer when the rectangular wire forthe second layer is started to be wound around the tooth insulatingportion.

[0130] According to the third aspect of the invention, since the degreeof freedom of direction in which the rectangular wire is introduced isexpanded, the degree of freedom in designing the insulating bobbin isincreased.

[0131] According to the fourth aspect of the invention, since the degreeof freedom of direction in which the rectangular wire is introduced isexpanded further, the degree of freedom in designing the insulatingbobbin is increased further.

[0132] According to the fifth aspect of the invention, when the firstturn of the rectangular wire is wound around the tooth insulatingportion, the rectangular wire can be wound therearound closely to theinner side of the extending portion without producing no gap between thewire and the inner side, thereby making it possible to increase thespace factor.

[0133] According to the sixth aspect of the invention, the rectangularwire of the second layer can ride over the rectangular wire of the firstlayer in a smooth fashion, thereby making it possible to prevent theoccurrence of a disturbance in winding.

[0134] According to the seventh aspect of the invention, there can beobtained the stator which can provide the extremely high space factor ofrectangular wire.

[0135] According to the eighth aspect of the invention, since the spacefactor can be increased and the widthwise movement of the rectangularwire wound around the outermost layer can be restricted by winding therectangular wire in an aligned fashion, the rectangular wire can bemaintained in the desired shape, thereby making it possible to increasethe reliability of the stator so fabricated.

[0136] According to the ninth aspect of the invention, the winding workcan be implemented more smoothly, and the insulating bobbin can beattempted to be made lighter in weight and lower in costs.

[0137] According to the tenth aspect of the invention, the space factorcan be increased, and the rectangular wire wound can be maintained inthe desired shape, thereby making it possible to enhance the reliabilityof the stator so fabricated.

What is claimed is:
 1. An insulating bobbin mounted on a tooth extendingfrom an annular yoke of a stator with a rectangular wire being aroundthe insulating bobbin, comprising: a tooth insulating portion insulatingthe tooth of the stator and the rectangular wire; and an extendingportion extending from an end portion of the tooth insulating portionalong an inner surface of the yoke, wherein a guide groove guiding therectangular wire diagonally relative to a circumferential direction ofthe tooth insulating portion from an outside of the extending portion isprovided in a side of the extending portion on one of axial sides of thestator.
 2. An insulating bobbin as set forth in claim 1, wherein aninclination angle of the guide groove relative to the circumferentialdirection of the tooth insulating portion is set equal to or larger thanan angle θ which is expressed by the following equation; θ=tan⁻¹(Ww/Wt)wherein Ww represents a width of the rectangular wire, and Wt representsa width of the tooth insulating portion.
 3. An insulating bobbin as setforth in claim 1, wherein a bottom surface of the guide groove is madeup of an inclined surface which inclines inwardly in the axial directionof the stator as the bottom surface approaches the tooth insulatingportion along a longitudinal direction of the guide groove.
 4. Aninsulating bobbin as set forth in claim 3, wherein the bottom surface ofthe guide groove is made up of an inclined surface which inclinesinwardly in the axial direction of the stator as the bottom surfaceapproaches the tooth insulating portion along a widthwise direction ofthe guide groove, and wherein the bottom surface of the guide grooveconnects continuously to a side of the tooth insulating portion withoutany difference in level.
 5. An insulating bobbin as set forth in claim1, wherein an intersection point between an inner side of the extendingportion and an outer side of the guide groove is positioned outwardly ofa side of the tooth insulating portion where the rectangular wire isbent for the first time by a distance equal to or larger than athickness of the rectangular wire.
 6. An insulating bobbin as set forthin claim 1, wherein a height of a highest point of a line ofintersection between a rectangular wire for a first layer and arectangular for a second wire is set equal to or smaller than a heightbeing 1.5 times as large as the thickness of the rectangular wire fromthe side of the tooth insulating portion.
 7. A stator, comprising: aninsulating bobbin mounted on a tooth extending from an annular yoke of astator with a rectangular wire being around the insulating bobbin,including: a tooth insulating portion insulating the tooth of the statorand the rectangular wire; and an extending portion extending from an endportion of the tooth insulating portion along an inner surface of theyoke, wherein a guide groove guiding the rectangular wire diagonallyrelative to a circumferential direction of the tooth insulating portionfrom an outside of the extending portion is provided in a side of theextending portion on one of axial sides of the stator, wherein the teethare provided of an annular yoke at predetermined intervals in acircumferential direction, wherein the insulating bobbin is mounted oneach of the teeth, and wherein a rectangular wire is wound around theinsulating bobbin.
 8. An insulating bobbin as set forth in claim 1,wherein the rectangular wire for an outermost layer is extendeddiagonally from a start-winding position thereof on one edge side of theinsulating bobbin toward the other edge side thereof to the followingline so as to straddle a space equivalent to one line so as to provide arecessed portion and then wound around a plurality of turns to form adiagonal extending portion, and thereafter is wound across the diagonalextending portion in a direction in which the rectangular wirediagonally intersects with the diagonal extending portion so as to bewound into the recessed portion.
 9. An insulating bobbin as set forth inclaim 1, wherein a chamfered portion is formed at a corner portion ofthe bobbin and a tapered portion is provided on an inside of thechamfered portion.
 10. A method for manufacturing a stator including aninsulating bobbin having a tooth insulating portion insulating the toothof the stator and the rectangular wire, an extending portion extendingfrom an end portion of the tooth insulating portion along an innersurface of the yoke and a guide groove guiding a rectangular wirediogonally relative to a circumferential direction of the toothinsulating portion from an outside of an extending portion on one ofaxial sides of the stator, comprising steps of: providing a plurality ofteeth on the stator at predetermined intervals in a circumferentialdirection thereof; mounting insulating bobbins on the plurality ofteeth; winding concentratedly a rectangular wire around the insulatingbobbin in an aligned fashion; causing a rectangular wire for anoutermost layer to extend diagonally from a start-winding positionthereof on one edge side of the insulating bobbin toward the other edgeside thereof to the following line so as to straddle a space equivalentto one line so as to provide a recessed portion and then winding therectangular wire a plurality of turns to form a diagonal extendingportion; and winding the rectangular wire so diagonally extended acrossthe diagonal extending portion in a direction in which the rectangularwire diagonally intersects with the diagonal extending portion so as tobe wound into the recessed portion.
 11. An insulating bobbin mounted ona tooth extending from an annular yoke of a stator with a rectangularwire being around the insulating bobbin, comprising: a tooth insulatingportion insulating the tooth of the stator and the rectangular wire; andan extending portion extending from an end portion of the toothinsulating portion along an inner surface of the yoke, wherein a guidegroove guiding the rectangular wire to the outside is provided in a sidewhere the end-winding end of the rectangular portion is located.